Decticus verrucivorus

behaviour · bio.acousti.ca

[Dense grass] tufts are also used by the males as song perches. Unlike many bush-crickets, they sing most in the early part of the day - from mid-morning to early afternoon, and only during warm weather. The song is usually delivered from a perch on a grass tussock, and takes the form of prolonged bursts of repeated high-pitched clicks. The rate of repetition increases to about 10 clicks per second within a minute or so of the start of a burst. The volume of the song is quite low, and for many observers a bat detector is needed to locate it at more than a few metres distance. Males are also reported to emit short isolated chirps.

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behaviour · bio.acousti.ca

The song is a sequence of 'tick'-sounds. These are at first hesitant, then followe each other ever more closely, but the individual syllables always remain clearly audible.

this account at bio.acousti.ca

behaviour · bio.acousti.ca

The calling song is quite uniform in most of western Europe, even where there are morphological differences, e.g. f. monspeliensis in southern France (Figs 227, 236, 245) (perhaps now extinct) and f. aprutianus in the Apennines (Figs 228, 237, 246). However, D. v. assiuus Ingrish, Willemse & Heller, which occurs in the high mountains of central Spain, has a markedly differnet song. Two separate accounts are therefore given below. Western Europe generally (Figs 224-228, 233-237, 242-246. Cd 1, track 27) The loud calling song, produced mainly on hot sunny days, consists of a long echeme-sequence, often lasting several (up to 5 or more) minutes, the sound being reminiscent of the loud ticking sound produced by older free-wheeling bicycles. The sequence begins with well-separated echemes, but these are repeated increasing rapidly untily they merge into a dense sequence with an echeme repetiuon rate of about 8-10/s (rarely slower, down to 6/s). Oscillographic analysis shows each echeme to be quite complex, consisiting of four syllables, grouped into two pairs. The initial opening of the fore wings at the beginning of teh echeme usually produces a distinct hemisyllable, which is sometimes quite loud; the remaining hemisyllables are quiet or absent. The first closing hemisyllable is usually quiet and occassionally absent or almost so; the remaining closing hemisyllables usually lasts 12-20 ms (rarely up to 30 ms) with an interval of about 5-10 ms between the two pairs. The second closing hemisyllable of each pair usually follows immediately, the pause between them being no more than 3 ms at most. The whole echeme, including the initial opening hemisyllable, usually lasts about 45-80 ms, but can be as short as 30 ms if the initial opening hemisyllable is absent. The interval between successive echemes, once a constant repetition rate has been reached, is ually 50-100 ms, but can be as short as 25 ms or as long as 150 ms. Males sometimes produce completely isolated echemes, aprticularly early in the day, but these are clearly not a fully developed calling song. D. v. assiduus (Figs 229-232, 238-241, 247-250. CD 1, track 28) The calling song is also loud and also produced in warm, sunny wather, as well as in cooler conditions. Typically it consists of long sequences of short echemes separated byvery brief pauses (Figs 229-231). The sequences begin rather like those of the more typical song of D. veruccivorus, with more widely spaced, short echemes of 3-6 syllables. The gaps between the syllables soon close up to about 50-100 ms and the echemes become longer, sometimes consisting of up to 30 or more syllable,s though varying greatly and often still including some short ones of 3-5 syllables. A sequence of this kind often lasts for several minutes. Sometimes, in cooler conditions, longer echemes are produced, lasting up to 20 s or more without pause (Fig. 232). The echemes differ markedly from those of typical D. verrucivorous in consiting of simple trains of identical, equally spaced syllables and in varying greatly in the number of syllables they contain. The syllable repetion rate is usually 30-40/s in warm sunny weather, but can be as low as 18/s in cooler conditions. Oscillographic analysis shows that opening hemisyllables are usually very quiet or absent and that the closing hemisyllables usually last about 12-15 ms in warm conditions, but up to 25 ms or more when cooler.

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